The long-term goal of the proposed research is to use the fruit fly, Drosophila melanogaster, as an animal model to unravel the mechanisms through which insects respond to sensory cues, ranging from changes in temperature to insect repellents. These questions are of potential relevance to the control of insect pests, since mosquitoes that spread diseases are attracted to humans through thermosensory, visual and chemical cues. Aversive temperatures and chemical repellents deter insects. Therefore, understanding the mechanisms underlying avoidance behavior may provide important insights into insect pest control. A key group of receptor proteins that sense environmental stimuli are Transient Receptor Potential (TRP) cation channels. Among the 13 Drosophila members, TRPA1 is of particular note as it is a detector for a wide array of noxious sensory inputs, including slightly warm or hot temperatures, insect repellents, and excessive light. Here, we propose to dissect the molecular, cellular and behavioral mechanisms through which TRPA1 allows larvae and adult flies to elude aversive stimuli. To accomplish our goals, we propose to employ a multidisciplinary approach, using a combination of molecular genetics, biochemistry, cell biology, electrophysiology and behavioral approaches. Aim 1 will test the hypothesis that bright light, which larvae avoid, activates TRPA1 through a novel mechanism of light detection that is independent of a cell surface protein. In Aim 2 we propose to test the hypothesis that TRPA1 functions as a detector that allow flies to use the daily changes in temperature to set circadian cycles of locomotor activity. The experiments proposed in Aim 3 will test hypotheses concerning the function and mechanism by which TRPA1 is activated via a thermosensory signaling cascade. This cascade represents a new mode of activation of TRP channels in contrast to the well-known direct activation of thermoTRPs by changes in temperature. Aim 4 is an outgrowth of the observation that TRPA1 is required for flies to avoid the insect repellent, citronellal, and this response occurs through both direct and indirect mechanisms in both mosquitoes and fruit flies. In the first part of this aim we will test the hypothesis that an additional TRPA channel functions in the aversive responses to other insect repellents (geraniol and camphor). The second part of aim 4 tests the hypothesis that G-protein coupled receptors detect repellents directly, and initiate signaling cascades that lead to indirect activation of TRP channels. The proposed studies ultimately could lead to the identification of a new generation of safer and more effective repellents to control insect-borne disease by identifying and characterizing molecular targets for such compounds.